In response to fuel efficiency concerns and desired performance characteristics, an emphasis has been placed on using electrical power to operate various components associated with a vehicle. Hybrid vehicles have been developed, for example, that rely on a combination of electric energy and energy produced by a traditional combustion engine to power certain electrical accessories and traction devices. One problem faced by hybrid vehicles results from the different power level requirements of the various electrically powered elements. Certain applications may require two or more power sources having different power level outputs to meet the needs of the electrical elements. Further, electrical buses for segregating the different power levels and for supplying power to the electrical elements may also be necessary.
Electrical systems including, for example, a low voltage power source combined with a higher voltage power source have been proposed to address these issues. For example, U.S. Pat. No. 6,580,180 to Tamai et al. (“the '180 patent”). discloses an electrical system that includes both a low voltage battery and a higher voltage battery. The low voltage battery may be used to operate low power devices, while the higher voltage battery may be used to operate higher power devices. The electrical system of the '180 patent also includes low and high voltage buses for carrying the different power levels to the various devices.
While the electrical system of the '180 patent may meet the power requirement needs of certain vehicles, this electrical system may be problematic and may not offer a desired level of operational flexibility. For example, the voltage level of the higher voltage battery (and associated bus) may be insufficient for operating certain high load devices such as HVAC units, electric pumps, air compressors, and other devices that may be found on trucks, work machines, and other types of vehicles. Further, the electrical system of the '180 patent is not configured for receiving power from outside sources. As a result, in order to operate the various devices for significant time periods without depleting the batteries, the engine must be running. Also, the buses of the electrical system of the '180 patent include no partitioning. Thus, there is no capability for energizing only a portion of a particular bus. Rather, each bus will be either fully energized or fully de-energized.
The present invention is directed to overcoming one or more of the problems or disadvantages existing with the electrical system architectures of the prior art.